Non-volatile memory device and method of manufacturing same

ABSTRACT

According to an embodiment, a non-volatile memory device includes a first conductive layer, electrodes, an interconnection layer and at least one semiconductor layer. The electrodes are arranged between the first conductive layer and the interconnection layer in a first direction perpendicular to the first conductive layer. The interconnection layer includes a first interconnection and a second interconnection. The semiconductor layer extends through the electrodes in the first direction, and is electrically connected to the first conductive layer and the first interconnection. The device further includes a memory film between each of the electrodes and the semiconductor layer, and a conductive body extending in the first direction. The conductive body electrically connects the first conductive layer and the second interconnection, and includes a first portion and a second portion connected to the second interconnection.The second portion has a width wider than the first portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. application Ser. No. 16/940,472 filedJul. 28, 2020, which is a continuation of U.S. application Ser. No.16/360,102 filed Mar. 21, 2019 (now U.S. Pat. No. 10,763,279 issued Sep.1, 2020), which is a continuation of U.S. application Ser. No.15/995,407 filed Jun. 1, 2018 (now U.S. Pat. No. 10,283,525 issued May7, 2019), which is a continuation of U.S. application Ser. No.15/679,301 filed Aug. 17, 2017 (now U.S. Pat. No. 10,043,821 issued Aug.7, 2018), which is a continuation of U.S. application Ser. No.14/643,056 filed Mar. 10, 2015 (now U.S. Pat. No. 9,773,803 issued Sep.26, 2017) and claims the benefit of priority from U.S. ProvisionalPatent Application 62/047,350 filed Sep. 8, 2014; the entire contents ofeach of which are incorporated herein by reference.

FIELD

Embodiments are generally related to a non-volatile memory device and amethod of manufacturing the same.

BACKGROUND

A NAND type non-volatile memory device has been developed, whichincludes a memory cell array of a three-dimensional structure. Thememory cell array includes, for example, word lines stacked on a sourcelayer, a channel body extending through the word lines, and a memorycell provided between each word line and the channel body. Moreover, forexample, an interconnection layer including a source line and a bit lineis provided on a side of the word lines opposite to a source layer.Then, the channel body is electrically connected to the source layer andthe bit line. In addition, the source layer is electrically connected tothe source line by a conductive body provided through the word lines.Thus, a NAND string that includes memory cells is provided along thechannel body.

In a manufacturing process of the memory cell array, a memory film and achannel body are formed in a memory hole that extends through the wordlines to the source layer. The memory film includes a charge storageportion between the word line and the cannel body, which serves as thememory cell. The memory film is also an insulation film whichelectrically insulates the word line and the channel body, and thus, aprocess of selectively removing the memory film at the bottom of thememory hole is necessary to electrically connect the channel body andthe source layer. In some cases, the channel body and the source layerare formed together, and the source layer that is formed under the wordlines is covered with the memory film. In such a case, a process ofselectively removing the memory film is also required to electricallyconnect the source layer and the source interconnection via theconductive body. Such a process may become more difficult as theminiaturization of the memory cell array progresses. That is, a processmargin for selectively removing the memory film becomes smaller, and thesmall margin may generate unintentional over-etching in other portions.Hence, a non-volatile memory device and a manufacturing method thereofare required, which provides a large process margin for selectivelyremoving the memory film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a non-volatile memorydevice according to a first embodiment;

FIG. 2 is a schematic view showing another cross section of thenon-volatile memory device according to the first embodiment;

FIGS. 3A to 11 are schematic cross-sectional views showing amanufacturing process of the non-volatile memory device according to thefirst embodiment;

FIGS. 12 to 16 are schematic cross-sectional views showing amanufacturing process of a non-volatile memory device according to avariation of the first embodiment; and

FIGS. 17 to 21 are schematic cross-sectional views showing amanufacturing process of a non-volatile memory device according to asecond embodiment.

DETAILED DESCRIPTION

According to an embodiment, a non-volatile memory device includes afirst conductive layer, electrodes, an interconnection layer and atleast one semiconductor layer. The electrodes are arranged in a firstdirection perpendicular to the first conductive layer. Theinterconnection layer is provided on a side of the electrodes oppositeto the first conductive layer, and the interconnection layer includes afirst interconnection and a second interconnection. The semiconductorlayer extends through the electrodes in the first direction. One end ofthe semiconductor layer is electrically connected to the firstconductive layer, and the other end of the semiconductor layer iselectrically connected to the first interconnection layer. The devicefurther includes a memory film provided between each of the electrodesand the semiconductor layer, and a conductive body extending in thefirst direction between the first conductive layer and the secondinterconnection. The conductive body electrically connects the firstconductive layer and the second interconnection, and includes a firstportion and a second portion. The first portion is connected to thefirst conductive layer, and the second portion is electrically connectedto the second interconnection and has a width wider than the firstportion in a second direction orthogonal to the first direction.

Hereinafter, embodiments will be described with reference to drawings.The same numeral is applied to the same portion in the drawings toappropriately omit a detailed description thereof, and a differentportion will be described. The drawings are schematic or conceptual,such that a relationship between a thickness and a width of eachportion, and a size ratio between portions are not necessarily the sameas real ones. Moreover, when representing the same portion, dimensionsand ratios are represented differently from each other by the drawings.

Moreover, an arrangement and a configuration of each portion will bedescribed by using an X axis, a Y axis, and a Z axis shown in eachdrawing. The X axis, the Y axis, and the Z axis are orthogonal to oneanother and represent an X-direction, a Y-direction, and a Z-direction,respectively. In addition, the Z-direction is described as upward and adirection opposite to the Z-direction is described as downward in somecases.

First Embodiment

FIG. 1 is a schematic cross-sectional view which shows a non-volatilememory device 1 according to a first embodiment.

FIG. 2 is a schematic view which shows another cross-section of thenon-volatile memory device according to the first embodiment. FIG. 2shows a structure of a cross-section taken along line A-A shown in FIG.1 .

A non-volatile memory device 1 includes a first conductive layer(hereinafter, source layer 10), electrodes, at least one semiconductorlayer (hereinafter, channel body 30), and a memory film 40. Theelectrodes include, for example, control gates 20, a selection gate 70,and a selection gate 80.

The electrodes are arranged in a first direction (hereinafter,Z-direction) which is perpendicular to the source layer 10. In addition,the electrodes extend in the Y-direction, respectively. The channel body30 extends through the electrodes in the Z-direction. The memory film 40is provided between each of the electrodes and the channel body 30. Amemory cell MC is provided between each control gate 20 and the channelbody 30.

The non-volatile memory device 1 further includes an interconnectionlayer 50. The interconnection layer 50 is provided on a side of theelectrodes opposite to the source layer 10. The interconnection layer 50includes first interconnections (hereinafter, bit lines 51), a secondinterconnection (hereinafter, source line 53), and an interlayerinsulation film 55. The bit lines 51 extend in, for example, theX-direction, and are disposed in parallel in the Y-direction.

One end of the channel body 30 is electrically connected to the sourcelayer 10, and the other end thereof is electrically connected to a bitline 51. In this example, a lower end of the channel body 30 is directlyconnected to the source layer 10. In other words, the channel body 30and the source layer 10 are formed together, and the channel body 30extends from the source layer 10 in the Z-direction.

An upper end of the channel body 30 is electrically connected to any oneof the bit lines 51. For example, the upper end of the channel body 30is electrically connected to the bit line 51 through a contact plug 57.

The selection gate 70 is provided between the source layer 10 and acontrol gate 20 a. The control gate 20 a is positioned at an end of thecontrol gates 20 on the source layer 10 side.

The selection gate 80 is provided between a control gate 20 b and theinterconnection layer 50. The control gate 20 b is positioned at an endof the control gates 20 on the interconnection layer 50 side.

The selection gates 70 and 80 act as a gate electrode which switchesON/OFF states of a selection transistor, and thus controls electricalconduction of the channel body 30, respectively.

Furthermore, the non-volatile memory device 1 includes a conductive body60. The conductive body 60 extends between the source layer 10 and thesource line 53 in the Z-direction, and electrically connects the sourcelayer 10 and the source line 53.

The conductive body 60 has a first portion 61 and a second portion 63.The first portion 61 is connected to the source layer 10. In otherwords, the first portion 61 is formed together with the source layer 10,and extends from the source layer 10 in the Z-direction. The firstportion 61 is provided to have a length shorter than an interval betweenthe source layer 10 and the selection gate 70 in the Z-direction.

The second portion 63 is electrically connected to the source line 53.For example, the second portion 63 is electrically connected to thesource line 53 through a contact plug 59. In addition, a width W₂ of thesecond portion 63 in the X-direction is wider than a width W₁ of thefirst portion 61 in the X-direction.

Specifically, the non-volatile memory device 1 includes a substrate 13,an interlayer insulation film 15, and a second conductive layer(hereinafter, back gate layer 17). The substrate 13 is, for example, asilicon substrate.

The source layer 10 is embedded in the back gate layer 17. For example,the memory film 40 is interposed between the source layer 10 and theback gate layer 17, and electrically insulates each other. The memoryfilm 40 is also interposed between the first portion 61 and the backgate layer 17, and electrically insulates each other.

As shown in FIG. 1 , a boundary between the first portion 61 and thesecond portion 63 is positioned at a level between the back gate layer17 and the selection gate 70 in the Z-direction. Here, “level” means aposition in the Z-direction, and indicates, for example, a height froman upper surface of the source layer 10.

As shown in FIG. 2 , the control gate 20 has, for example, a rectangularshape extending in the Y-direction. The control gate 20 is disposed inparallel in the X-direction. The conductive body 60 is provided betweenadjacent control gates 20 in the X-direction. An insulation film 65 isprovided between the control gate 20 and the conductive body 60, andelectrically insulates each other.

The non-volatile memory device 1 includes channel bodies 30 extendingthrough the control gates 20 in the Z-direction. The channel body 30 hasa cross section of a circular shape perpendicular to the Z-direction,for example. The memory film 40 is provided between the control gate 20and the channel body 30. Then, a memory cell MC is provided between thecontrol gate 20 and the channel body 30.

Moreover, the channel body 30 is disposed at a connectable positionthrough the contact plug 57 in any one of the bit lines 51 disposed inparallel in the Y-direction. For example, FIG. 1 is a cross-sectiontaken along line B-B shown in FIG. 2 .

Then, a method of manufacturing the non-volatile memory device 1according to the first embodiment will be described referring to FIGS.3A to 11 . FIGS. 3A to 11 are schematic cross-sectional views eachshowing a manufacturing step of the non-volatile memory device 1.

As shown in FIG. 3A, a wafer is prepared in which the interlayerinsulation film 15, the back gate layer 17, and an insulation film 21are sequentially formed on the substrate 13. The substrate 13 is, forexample, a silicon substrate. For example, an integrated circuit may beformed on an upper surface 13 a of the substrate 13 to control a memorycell array.

The back gate layer 17 is, for example, a polycrystalline silicon(poly-silicon) layer doped with P-type impurities. A sacrificial layer103 is embedded in the back gate layer 17. The sacrificial layer 103 is,for example, a non-doped poly-silicon layer, which is not intentionallydoped with impurities. The sacrificial layer 103 has, for example, arectangular parallelepiped shape, extending through the back gate layer17 in the Y-direction. The insulation film 21 provided on the back gatelayer 17 is, for example, a silicon oxide film.

As shown in FIG. 3B, a slit 105 is formed to have a depth of reachingthe sacrificial layer 103 from an upper surface 21 a of the insulationfilm 21. The slit 105 is a groove extending in the Y-direction. The slit105 is formed by using, for example, a reactive ion etching (RIE) and byselectively etching the insulation film 21 and an upper portion 17 a ofthe back gate layer 17.

As shown in FIG. 3C, a sacrificial layer 107 is formed in the slit 105.The sacrificial layer 107 is, for example, made of the same material asthe sacrificial layer 103. Specifically, the non-doped poly-siliconlayer is formed on a wafer having the slit 105, and embeds the slit 105.Then, the poly-silicon layer on the wafer is etched until the uppersurface 21 a of the insulation film 21 is exposed, thus leaving aportion of the poly-silicon layer embedded in the slit 105.

As shown in FIG. 4 , a protective film 109 is selectively formed, andcovers the exposed portion of the sacrificial layer 107 in the uppersurface 21 a of the insulation film 21. The protective film 109 is, forexample, a tantalum oxide film or an amorphous silicon film. Then, aninsulation film 22 is formed on the insulation film 21 and theprotective film 109. The insulation film 22 is, for example, a siliconoxide film. As a result, an insulation film 23 is formed as a firstlayer on the back gate layer 17. The insulation film 23 includes theinsulation film 21 and the insulation film 22.

Then, a conductive film 113 and an insulation film 25 are sequentiallyformed on the insulation film 23. The conductive film 113 is, forexample, a conductive poly-silicon film. The insulation film 25 is, forexample, a silicon oxide film.

Subsequently, a conductive film 115 and an insulation film 27 arealternately stacked on the insulation film 25. The conductive film 115is, for example, a conductive poly-silicon film. The insulation film 27is, for example, a silicon oxide film. The number of stacked layers ofthe conductive film 115 is the same as the number of memory cells MCdisposed in the Z-direction along the channel body 30.

Further, a conductive film 117 and an insulation film 29 aresequentially formed on an insulation film 27 a. The insulation film 27 ais positioned at an upper end of the insulation films 27 stacked in theZ-direction. The conductive film 117 is, for example, a conductivepoly-silicon film. The insulation film 29 is, for example, a siliconoxide film.

As shown in FIG. 5 , a slit 121 and a memory hole 123 are formed throughthe stacked structure. The slit 121 and the memory hole 123 are formedby using, for example, RIE. The slit 121 is a groove that has a depth ofreaching the protective film 109 from an upper surface 29 a of theinsulation film 29, and extends in the Y-direction. The slit 121 dividesthe conductive film 113, the conductive film 115, and the conductivefilm 117 into the selection gate 70, the control gate 20, and theselection gate 80, respectively.

The memory hole 123 has, for example, a circular opening, and has adepth of reaching the sacrificial layer 103 from the upper surface 29 aof the insulation film 29. The memory hole 123 may extend through thesacrificial layer 103. In addition, an opening diameter W₃ of the memoryhole 123 is smaller than a width W₂ of the slit 121 in the X-direction.The opening diameter W₃ of the memory hole 123 is the same as, forexample, a width W₁ of the sacrificial layer 107 in the X-direction, forexample.

The memory hole 123 and the slit 121 are preferably formed at the sametime. For example, the protective film 109 exposed at a bottom surfaceof the slit 121 serves as an etching stop film. That is, the slit 121 isnot etched deeper than a position of the protective film 109, while thememory hole 123 is etched to a depth of reaching the sacrificial layer103.

Then, the protective film 109 is selectively removed via the slit 121.Subsequently, as shown in FIG. 6 , the sacrificial layer 103 and 107 areselectively removed, for example, by wet etching using an alkalisolution. Then, a space 103 x is formed after removing the sacrificiallayer 103, and the slit 105 is reopened.

As shown in FIG. 7 , the memory film 40, a semiconductor film 130 and acore 140 are formed inside the slits 105 and 121, the memory hole 123,and a space 103 x.

For example, the memory film 40 is formed using a low-pressure ChemicalVapor Deposition (CVD) method or an Atomic Layer Deposition (ALD) methodso as to cover the inner surfaces of the slits 105 and 121, the memoryhole 123, and the space 103 x. The memory film 40 has a structure inwhich a silicon oxide film, a silicon nitride film, and a silicon oxidefilm are successively stacked, for example.

Then, the semiconductor film 130 is formed on the memory film 40. Thesemiconductor film 130 is, for example, a poly-silicon film, and isformed using the low-pressure CVD method or the ALD method.Subsequently, the core 140 is formed on the semiconductor film 130. Thecore 140 is, for example, a silicon oxide film, and is formed by thelow-pressure CVD method or the ALD method.

The memory film 40, the semiconductor film 130, and the core 140 areformed to fill the slit 105, the memory hole 123 and the space 130 x. Incontrast, the memory film 40, the semiconductor film 130, and the core140 are formed in the slit 121, leaving a space 121 a therein. That is,it is possible to make the space 121 a in the slit 121 by setting awidth W₂ of the slit 121 wider than a width W₁ of the slit 105 and adiameter W₃ of the memory hole 123.

As shown in FIG. 8 , by etching the memory film 40, the semiconductorfilm 130, and the core 140, the portions thereof on the insulation film29 and in the slit 121 are removed.

The memory film 40, the semiconductor film 130, and the core 140 arepreferably etched by using, for example, an isotropic etching methodsuch as a wet etching, a chemical dry etching, or the like. Thus,etching the first portion of the memory film 40, the semiconductor film130, and the core 140 on the upper surface 29 a of the insulation film29, and etching the second portion thereof in the slit 121 via the space121 a may proceeds from the core 140 to the memory film 40 prior toetching the third portions embedded in the memory holes 123 and the slit105. Then, it is possible to leave the third portions in the slit 105and the memory holes 123 by stopping the etchings when the first andsecond portions are removed.

As shown in FIG. 9 , each end portion of the control gate 20, and theselection gates 70 and 80, which is exposed in the slit 121, issilicided to reduce resistance thereof.

For example, a nickel film is formed, which covers the insulation film29 and the inner surface of the slit 121. Subsequently, a heat treatmentis performed on the wafer at a predetermined temperature to form anickel silicide by using reaction of the poly-silicon and the nickelfilm. Then, parts of nickel film covering the insulation film 23 exposedat the bottom of the slit 121, end surfaces of the insulation films 25and 27, and the insulation film 29 are removed. Thus, the silicidedportions 20 s, 70 s and 80 s are formed at the ends of the control gate20, the selection gate 70, and the selection gate 80 respectively.

In addition, a silicided portion 130 s is formed at an upper end of thesemiconductor film 130 embedded in the slit 105 and an upper end of thesemiconductor film 130 embedded in the memory hole 123, respectively.

As shown in FIG. 10 , an insulation film 65 is formed on an inner wallof the slit 121. The insulation film 65 is, for example, a silicon oxidefilm formed by using the CVD method. For example, a silicon oxide filmis formed to cover the insulation film 29 and an inner surface of theslit 121. Then, for example, parts of the silicon oxide film coveringthe bottom surface of the slit 121 and an upper surface 29 a of theinsulation film 29 are removed by using an anisotropic RIE method,leaving a portion of the insulation film 65 on a side wall of the slit121.

As shown in FIG. 11 , a metal film 150 is embedded in the slit 121. Themetal film 150 is, for example, a tungsten (W) film formed by using theCVD method. For example, the metal film 150 is formed in a followingorder. A tungsten film is formed to cover the insulation film 29 and tobe embedded in the slit 121. Then, the tungsten film is etched by usinga dry etching method to remove a portion provided on the insulation film29, leaving a portion thereof embedded in the slit 121. Thus, the metalfilm 150 is formed in the slit 121. In addition, the metal film 150 mayhave a two-layer structure which includes a barrier metal layer of atitanium nitride (TiN), for example, and tungsten layer, wherein thebarrier layer is in contact with the inner surface of the slit 121.

Then, the interconnection layer 50 is formed on the insulation film 29to complete the non-volatile memory device 1.

The semiconductor film 130 has a first part, a second part and a thirdpart. The first part of the semiconductor film 130 is embedded in thememory hole 123, and serves as the channel body 30. The second part ofthe semiconductor film 130 is embedded in the space 103 x formed byremoving the sacrificial layer 103, and serves as the source layer 10.The third part of the semiconductor film 130 is embedded in the slit105, and serves as a first portion 61 of the conductive body 60. Themetal film 150 embedded in the slit 121 is a second portion 63 of theconductive body 60. A silicided portion 130 s may be preferablyinterposed between the first portion and the second portion 63 to reducea contact resistance therebetween.

In the embodiment, the first portion 61 of the conductive body 60 is incontact with the source layer 10, and enlarges the process margin forremoving the memory film 40 as follows. Thus, it may become possible toimprove a manufacturing yield by suppressing, for example, an openfailure between the source layer 10 and the source line 53 or a shortcircuit failure between the control gate 20 and the source line 53.

In the process step shown in FIG. 8 , the first portion 61 is formed byetching the memory film 40, the semiconductor film 130, and the core140. In this step, the first portion 61 is formed with variation in theupper end position thereof due to unevenness of an etching amount, andsuch a variation may reduce the process margin. For example, an upperend of the first portion 61 is set downward by over-etching thesemiconductor film 130. Further, while removing the memory film 40 thatcovers an inner surface of the slit 121, the insulation film 23 may alsobe etched, and an upper surface of the insulation film 23 is setdownward between the back gate layer 17 and the selection gate 70,facilitating the over-etching of the semiconductor film 130. As aresult, the upper end position of the first portion 61 is varieddepending on the etching condition.

The upper end of the first portion 61 is preferably positioned at alevel between the back gate layer 17 and the selection gate 70 in theZ-direction, for example. Thus, a thickness of the insulation film 23 inthe Z-direction may be set to absorb the variation width of the upperend position of the first portion 61. Thereby, it becomes possible toenlarge the process margin for etching the memory film 40, thesemiconductor film 130 and the core 140.

Then, a method of manufacturing the non-volatile memory device 1according to a variation of the first embodiment will be describedreferring to FIGS. 12 to 16 . FIGS. 12 to 16 are a schematiccross-sectional views which show another method for manufacturing thenon-volatile memory device 1.

For example, after etching the memory film 40, the semiconductor film130, and the core 140 as shown in FIG. 8 , an insulation film 125 isformed to cover the inner surface of the slit 121 and the insulationfilm 29 as shown in FIG. 12 .

The insulation film 125 is, for example, a silicon oxide film formedusing a plasma CVD method. For example, by using the plasma CVD method,it becomes possible to form the insulation film 125 that has a portion125 a on the bottom surface of the slit 121, a portion 125 b on theinner wall of the slit 121 and a portion 125 c on the insulation film29, wherein the portions 125 a and 125 c are thicker than the portion125 b.

As shown in FIG. 13 , the insulation film 125 is etched until the innerwall of the slit 121 is exposed. By using an isotropic etching method,such as a Chemical Dry Etching (CDE) method, the portion 125 b formed onthe inner wall of the slit 121 is removed. Since the portion 125 a andthe portion 125 c are thicker than the portion 125 b , it may bepossible to leave the portion 125 a on the bottom surface of the slit121 and the portion 125 c on the insulation film 29.

As shown in FIG. 14 , each end portion of the control gate 20, theselection gates 70 and 80, which is exposed in the slit 121, issilicided to reduce the resistance of the control gate 20, and theselection gates 70 and 80.

For example, the silicided portions 20 s, 70 s and 80 s are formedrespectively in the end portions of the control gate 20, the selectiongate 70, and the selection gate 80 by forming a nickel film covering theinner surface of the slit 121 and performing heat treatment thereon.

As shown in FIG. 15 , the insulation film 125 is removed. Subsequently,for example, an N-type impurity is ion-implanted into the exposedportions of the semiconductor film 130 at the bottom of the slit 121 andin the upper surface 29 a of the insulation film 29. A vapor-phasedoping of an N-type impurity may be performed instead of theion-implantation. A phosphorus (P) may be used as the N-type impurity,for example.

As shown in FIG. 16 , the insulation film 65 is formed on the inner wallof the slit 121. For example, a silicon oxide film is formed to coverthe insulation film 29 and the inner surface of the slit 121. Then, thesilicon oxide film formed on the bottom surface of the slit 121 and theupper surface 29 a of the insulation film 29 is removed by using, forexample, an anisotropic RIE method, leaving a part of the silicon oxidefilm as the insulation film 65 on the inner wall of the slit 121.

Subsequently, as shown in FIG. 11 , a metal film is embedded in the slit121, and the interconnection layer 50 is formed on the insulation film29 to complete the non-volatile memory device 1.

In this example, the insulation film 125 is formed on the bottom surfaceof the slit 121 and the upper surface 29 a of the insulation film 29 toprevent an upper end of the semiconductor film 130 embedded in the slit105 and an upper end of the semiconductor film 130 embedded in thememory hole 123 from being silicided. Then, a diffusion region 130 ndoped with the N-type impurity is formed at each end of thesemiconductor film 130. For example, by optimizing a concentration and aprofile of the N-type impurity in the diffusion region 130 n, it becomespossible to improve data erase characteristics of a NAND string that isprovided in the memory hole 123.

Second Embodiment

A method of manufacturing the non-volatile memory device 1 according toa second embodiment will be described referring to FIGS. 17 to 21 .FIGS. 17 to 21 are schematic cross-sectional views which represent theother manufacturing process of the non-volatile memory device 1.

As shown in FIG. 17 , the insulation film 125 is formed on the bottomsurface of the slit 121 and on the insulation film 29. In this example,sacrificial films 201, 203, and 207 are formed in place of the controlgate 20, the selection gates 70 and 80 shown in FIG. 13 . Thesacrificial film 201, 203, and 207 are, for example, a silicon nitridefilm. That is, a silicon oxide film and a silicon nitride film arealternately stacked on the back gate layer 17.

As shown in FIG. 18 , the sacrificial films 201, 203, and 207 areselectively removed. For example, the sacrificial films 201, 203, and207 are removed by a wet etching, for example, via the slit 121. Forexample, it is possible to selectively remove the silicon nitride filmusing a hot phosphoric acid as an etching solution without etching thesilicon oxide film.

As shown in FIG. 19 , a control gates 220, selection gates 270 and 280are formed in spaces 201 x, 203 x, and 207 x formed by removing thesacrificial films 201, 203, and 207. The control gates 220, theselection gates 270 and 280 are a metal film, for example.

For example, a tungsten film is formed in the spaces 201 x, 203 x, and207 x via the slit 121. The tungsten film is formed by using the CVDmethod, for example. In addition, the control gates 220 and theselection gates 270 and 280 may have a two-layer structure whichincludes, for example, a titanium nitride (TiN) and tungsten.

As shown in FIG. 20 , the insulation film 125 is removed. Then, theN-type impurity, for example, is ion-implanted into the exposed portionsof the semiconductor film 130 in the bottom portion of the slit 121 andin the upper surface 29 a of the insulation film 29. Instead of theion-implantation, the vapor-phase doping of the N-type impurity may beperformed.

As shown in FIG. 21 , the insulation film 65 is formed on the inner wallof the slit 121. Subsequently, a metal film is embedded in the slit 121through the process shown in FIG. 11 . Furthermore, the interconnectionlayer 50 is formed on the insulation film 29 to complete thenon-volatile memory device 1.

In this example, the metal film is used as the control gates 220 and theselection gates 270 and 280. Accordingly, the electric resistance of thecontrol gate 220 and the selection gates 270 and 280 is reduced, and anoperation speed of the memory cell MC is improved. In addition, thediffusion region 130 n doped with the N-type impurity is formed at theupper end of the semiconductor film 130 embedded in the slit 105 and theupper end of the semiconductor film 130 embedded in the memory hole 123,thereby improving the erase characteristics of the NAND string.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. A non-volatile memory device comprising: asubstrate; an interlayer insulating film provided above the substrate; afirst conductive layer provided above the interlayer insulating film; anupper interconnect structure including a first interconnection;electrodes provided between the first conductive layer and the upperinterconnect structure, the electrodes being arranged in a firstdirection perpendicular to the first conductive layer to constitute astacked body and functioning control gates for memory cells;semiconductor bodies extending through the electrodes in the firstdirection, one end of one of the semiconductor bodies being electricallyconnected to the first conductive layer, and the other end of the one ofthe semiconductor bodies being electrically connected to the firstinterconnection; a conductive body electrically connected to the firstconductive layer, the conductive body including a metal portionextending through the electrodes in the first direction and in a seconddirection orthogonal to the first direction between the first conductivelayer and the upper interconnect structure; and an insulation filmcovering side surfaces of the metal portion in a third directionorthogonal to the first direction and the second direction andinsulating between the metal portion and the respective electrodes, theconductive body including a first part proximal to the first conductivelayer and a second part distal to the first conductive layer, the secondpart having a width wider than a width of the first part along the thirddirection.
 2. The device according to claim 1, wherein the metal portioncontains tungsten.
 3. The device according to claim 1, wherein thesemiconductor body has a circular shape in a cross section orthogonal tothe first direction and a core film is provided inside the circularshape semiconductor body.
 4. The device according to claim 3, whereinthe core film is insulative.
 5. The device according to claim 1, whereineach of the electrodes extends in the second direction.
 6. The deviceaccording to claim 5, wherein the first interconnection extends in thethird direction.
 7. The device according to claim 1, wherein each of theelectrodes is a polycrystalline silicon film or a metal film.
 8. Thedevice according to claim 1, wherein the first conductive layerfunctions a source layer.
 9. The device according to claim 1, whereinthe first conductive layer includes a polycrystalline silicon film. 10.The device according to claim 1, wherein the semiconductor body has acircular shape in a cross section orthogonal to the first direction andan outer diameter of the circular shape semiconductor body is smallerthan the width of the first part of the metal portion at a certain levelincluded in one of the electrodes in the first direction.
 11. Anon-volatile memory device comprising: a substrate; an interlayerinsulating film provided above the substrate; a first conductive layerprovided above the interlayer insulating film; an upper interconnectstructure including a first interconnection; electrodes provided betweenthe first conductive layer and the upper interconnect structure, theelectrodes being arranged in a first direction perpendicular to thefirst conductive layer to constitute a stacked body and functioningcontrol gates for memory cells; semiconductor bodies extending throughthe electrodes in the first direction, one end of one of thesemiconductor bodies being electrically connected to the firstconductive layer, and the other end of the one of the semiconductorbodies being electrically connected to the first interconnection; aconductive body electrically connected to the first conductive layer,the conductive body including a metal portion extending through theelectrodes in the first direction and in a second direction orthogonalto the first direction between the first conductive layer and the upperinterconnect structure; and an insulation film covering side surfaces ofthe metal portion in a third direction orthogonal to the first directionand the second direction and insulating between the metal portion andthe respective electrodes, a number of the semiconductor bodies beingmore than a number of the conductive body, and the conductive bodyincluding a first part proximal to the first conductive layer and asecond part distal to the first conductive layer, the second part havinga width wider than a width of the first part along the third direction.12. The device according to claim 11, wherein the metal portion containstungsten.
 13. The device according to claim 11, wherein thesemiconductor body has a circular shape in a cross section orthogonal tothe first direction and a core film is provided inside the circularshape semiconductor body.
 14. The device according to claim 13, whereinthe core film is insulative.
 15. The device according to claim 11,wherein each of the electrodes extends in the second direction.
 16. Thedevice according to claim 14, wherein the first interconnection extendsin the third direction.
 17. The device according to claim 11, whereineach of the electrodes is a polycrystalline silicon film or a metalfilm.
 18. The device according to claim 11, wherein the first conductivelayer functions a source layer.
 19. The device according to claim 11,wherein the first conductive layer includes a polycrystalline siliconfilm.
 20. The device according to claim 11, wherein the semiconductorbody has a circular shape in a cross section orthogonal to the firstdirection and an outer diameter of the circular shape semiconductor bodyis smaller than the width of the first part of the metal portion at acertain level included in one of the electrodes in the first direction.